This invention relates to gamma-gamma density logging and more particularly to the correction of density logs obtained from radioactive zones in subsurface formations for the effects of natural gamma radiation from the radioactive materials.
In gamma-gamma density logging, formations surrounding a borehole are irradiated with gamma rays. These gamma rays are scattered through the formation and those returning to the borehole are detected. The count rate of gamma rays detected are recorded as a density log of the formation surrounding the borehole.
However, in formations of high natural gamma-ray activity, such as uranium ore formations, the high intensity of natural gamma rays from the formation adds to the intensity of gamma rays that would otherwise reach the detector. Such additional gamma rays result in a gamma-ray count rate indicative of an erroneous density that is lower than the actual density.